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A couple of questions about testing 12AX7 tubes.

I have been testing a bunch of RCA and some Fisher 12AX7 tubes on a Hancock tester at the local Antique Radio Museum. Two things happened while testing the tubes that I am not sure about.
The first thing that happened is that 3 of the tubes (out of the 15 that I tested) glow bright right after plugging them into the Hancock tube tester, then the immediately go down to the normal tube glow. Does this indicate a bad tube? One of the RCA long plates and two of the Fishers did this.
The second question is that while testing the triodes of 2 tubes the meter went all the way to the right and was pinned on the meter, which goes up to 3000. On one of the tubes both triodes pinned, on the other tube one triode pinned and the other read around 2800. Is this good or bad? Do I just have excellent tubes or is there something wrong with them?
Thanks for your help.
Joe
jbcello

Showing 1 response by jbcello

jbcello OP
25 posts
 
Thanks for both of your answers. Yes, I do agree that the only way to know you have a good pair of tubes is to listen to them. The reason I test the tubes is to try get pairs of them that closely match for my phono section in my Magus preamp. I assume that the better they are matched the more accurate the sound will be coming from both channels. Although I must admit my knowledge about tubes is very limited.
thanks,
Joe
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